Coating composition



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Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE FRANCIS B. MORTON, OFPAR-LIN, NEW JERSEY, ASSIGNOR TO E. I. DU PONT DE NEMOURS & COMPANY, OFWILMINGTON, DELAWARE, A CORPORATION OF DELA- WARE COATING COMPOSITION NoDrawing. Application filed June 27,

This invention relates to coating compositions and more particularly toa coating composition for leather, imitation leather, and the like.

A pigmented finish for leathers was developed during the recent war, dueto the shortage of dyestuffs for coloring leather encountered at thattime. It was composed of pigments of maximum hiding power incorporatedin alkaline solutions of shellac or casein to which were added variousother ingredients, such as wax emulsions, albumen, water soluble oilsand glycerine. By the use of this pigmented finish a uniform color wasobtained on the leather, whereas a dyed leather was not uniform in colordue to the fact that some portions of the leather absorbed more dyethanothers. In addition, the pigmented finish covered stains andblemishes so that leather which was formerly suited only for blackscould be used for other colors. This pigmented finish was, however,seriously defective in that it rubbed off easily on a wet cloth sincethe binder was soluble in water, and in many cases the finish produceda. brittle film on the leather which easily cracked off. More recentlythere has been used a nitrocellulose pigmented finish for grain leather,applied by spraying, in which a mixture of nitrocellulose and suitablesofteners is substituted as a binder in place of the water solublebinders used in the original type of pigmented finish. Thisnitrocellulose finish is objectionable in that its properties are suchthat it cannot be ironed out with a hot flat iron, nor can it be glazedwith a glazing machine. Still more recently, these objections wereovercome by the incorporation of adherent oils, such as neats-foot oil.However, although such films containing adherent oils showed a markedimprovement in quality over prior art finishes in all respects, it wasfelt that the adhesive properties were not the maximum obtainable, sincein some instances there was a tendency toward stripping from the basematerial.

This invention has as an object the production of a finish for leather,imitation leather, and the like which is not water soluble and whichmaybe ironed with a hot flat iron and 1928. Serial No. 288,808.

glazed with a glazing machine without inurious results to the finish. Afurther obect is the production of such a finish which will haveimproved qualities of adhesion. Other objects will appear hereinafter.

These objects are accomplished by the fol lowing invention whichconsists in adding or ganic acids to the nitrocellulose finishcontaining an adherent oil.

I have discovered that a finish having improved qualities of adhesionmay be obtained by the addition of organic acids, such as lactic acid.The following formulae represent a preferred composition at sprayingconsistency and the range for the materials at which a workable finishcan be obtained Color coat Range Per cent by weight Per centlhtrocellulosav 2.5 2. 5, Neats-Ioot oil l i 5.0 1 to 8 Dibutylphthalate 1. 5 0 to 2.5 85% lactic acid. s. 3, 1 1 to 10 Pigment or dye5, 0 0.1 to 10 Clear top coat Range n 7 Per cent by weight Per c-mtNitrocellulose M 2.5 2.5 Neat's-ioot oil 2. 5 1 to 8 75% lactic acid 3.1 1 to 10 The lactic acid is a. solution of lactic acid in water and inplace of lactic acid Imay use other organic acids, such as formic acid,tartaric acid, acetic acid, oxalic acid, or any other acid or substancethat acts as an acid.

The range for the amount of nitrocellulose in the above compositionswill depend on its viscosity and the method of application, and may befrom 1 to 10. Compositions are, therefore, base on 2.5% nitrocellulose,as the ratio of the non-volatile ingredients is an important factor. Theamount of pigment will depend on the type used, its oil absorptionvalue, its hiding power and the effect which is desired. Whentransparency, or socalled depth of finish, is desired lakes or even dyesmay be used. The pigments should preferably be inert in their actiontowards nitrocellulose and resistant to fading on exposure to light-f Inthe example given above,

dibutyl phthalate is not absolutely essential, its presence being due tothe fact that the pigment may be ground on colloid rolls in the samemanner as pigment is incorporated in celluloid, by grinding in a plasticof dibutyl phthalate and nitrocellulose, which method gives extremelygood dispersion. The pigment may also be ground on buhr mills or rollermills in part or all of the neats-foot oil in the manner customary inthe paint industry. The ratio of pigment to colloid or oil duringrinding will depend on the character of the pigment and the particularcolloid or oil used, as is well known to those skilled in the art. It isnot necessary that the adherent oil be the only oil present. Castor, raeseed, linseed, or other animal or vegeta le oils may be present, solong as there is sufiicient adherent oil to counteract the effect ofthese oils, which used alone produce a finish which cannot besuccessively glazed or ironed. Also more dibutyl phthalate or othercellulose plasticizer than 1s required to make a suitable colloid may bepresent with the adherent oil. In such cases, the pigment Ethy,

ma' be ground on buhr mills or other mills wit part or all of such oilsor plasticizers. In place of neats-foot oil, I may use other oils which,for the sake of convenience, I term adherent oils. These arespecifically cod liver, sperm, lard, olive, egg and a mixture ofcocoanut and paraffin oils. It is to be understood that the termadherent oils is meant to include the specific oils mentioned and isused for lack of a group classification which covers all these oils.

It is not absolutely essential to use adherent oil in all of the coats,but only in the top coat, since stickiness is due to the condition ofthe surface. For example, a top coat of clear or enamel containingneats-foot oil may be used over nitrocellulose colored coats of the oldtype. They may also be used over the water soluble type of colored coatbut, due to deficient adhesion, the nitrocellulose type of coloredbottom coat is to be preferred. The lactic acid may be used in coatingcompositions containing nitrocellulose, with or without oils orplasticizers, but those coating compositions containing an adherent oilWill be found superior. It has been found that the adhesion of the clearor pigmented finish to the leather may be improved by Washing theleather with lactic acid, or any other of the above mentioned acids,before applying the finish, in which case it is not necessary to add theacid to the finish. This method, however, does not produce as goodresults as when the acid is added to the finish.

The preferred nitrocellulose colored and clear coats may be made intofinished mixtures by the customary methods employed in the lacquer andenamel industry. The colors are ground in a nitrocellulose plastic andthe ground stock is then dissolved in suitable mixers with a thinnercontaining active solvents and diluents. The clear solutions are made bydissolving nitrocellulose in suitable mixers with a mixture of activesolvents and diluents and adding the proper amount of ad herent oil.Clear solutions ma also be made from concentrated solutions 0nitrocellulose by adding the proper amount of thinner and adherent oil.The following formula: represent a preferred enamel and a clearsolution:

Enamel Per cent by weight *Red enamel- 95.24 85% lactic acid i 4.76

' Red enamel Nitrocellulose plastic Per cent Per cent Indian red lronoxide plg- N itroeellulose 43. inept 11.11 Dibutyl phthalate 20.2)Nitrocellulose plastic.. 8. 56 Denatured alcohol 30. 10 Neats-Ioot oilmF.

.40 MIND .16 .63 .15

Clear solution Per cent by welght *Clear solut1on 95.25 85% lactic ac1di 4.75

' Clear solution N ltxocellulose baa Per cent Per cm! Nitrocellulosebase e3. 50 Ethyl acetate 43 20 Neats-(oot oil-20 F-- 4.00 Butylacetate.-. 10.00 Ethyl acetate 20. (X) Toluol 22 50 we (I) The abovefinishes may preferably be applied in two coats, one colored coatfollowed by a clear coat, and they should be applied by spraying as thismethod is found to be the most practicable one.

. While in the examples I have described nitrocellulose compositions, myinvention may be utilized in compositions containing any cellulosederivative.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim: r

l. A coating'composition which contains nitrocellulose, neats-foot oiland lactic acid in proportions such that when applied to leather anddried the composition willform its a non-tacky, strongly adherent filmwhich can be ironed with a hot iron and glazed in a glazing machine. 7

2. A coating composition which contains nitrocellulose, neats-foot oil,a plasticizer and lactic acid in proportions such that when applied toleather and dried the composition will form a non-tacky, stronglyadherent film which can be ironed with a hot iron and glazed in aglazing machine.

8. A coating composition which contains nitrocellulose, neats-foot oil,a pigment and lactic acid in proportions such that when applied toleather and dried the composition will form a non-tacky, stronglyadherent film which can be ironed with a hot iron and glazed in aglazing machine.

A. A coating composition which contains nitrocellulose, neatstoot oil, aplasticizer, a pigment and lactic acid in proportions such that whenapplied to leather and dried the composition will form a non-tacky,strongly adherent film which can be ironed with a hot iron and glazed ina glazing machine.

5. A coating composition which comprises a cellulose compound, an oilfrom the group consisting of neats-foot, cod liver, sperm, lard, olive,egg, and a mixture of cocoanut and paraflin oils, and an organic acid,said ingredients being in proportions such that when applied to leatherand dried the composition Will form a non-tacky, strongly adherent filmwhich can be ironed with a hot iron and glazed in a glazing machine.

6. A coating composition which comprises a cellulose ester, an oil fromthe group consisting of neats-foot, cod liver, sperm, lard, olive, egg,and a mixture of cocoanut and paraflin oils, and an organic acid, saidingredients being in proportions such that when applied to leather anddried the composition will form a non-tacky, strongly adherent filmwhich can be ironed with a hot iron and glazed in a glazing machine.

7. A coating composition which comprises nitrocellulose, an oil from thegroup consisting of neats-foot, cod liver, sperm, lard, olive, egg, anda mixture of cocoanut and paraifin oils, and an organic acid, saidingredients being in proportions such that when applied to leather anddried the composition will form a non tacky, strongly adherent filmwhich can be ironed with a hot iron and glazed in a glazing machine.

8. A coating composition which comprises nitrocellulose, an oil from thegroup consisting of neats-foot, cod liver, sperm, lard, olive, egg, anda mixture of cocoanut and paraflin oils, and an organic acid from thegroup including lactic, formic, tartaric. acetic and oxalic acids, thesaid ingredients being in proportions such that when applied to leatherand dried the composition will form a non-tacky, strongly adherent film

